#include "header.h"
char *f(char a[],int d, int c, int n)
{
    char *s;
    s=(char*)malloc((c-d+1)*sizeof(char));
    int i,j=0;
    
    if(d+c>n||n<0) printf("NULL");
    else for(i=d;i<d+c;i++)
         {
                           // printf("%c",a[i]);
                            *(s+j)=a[i];
                            j++;            
                           }
  return s;
}

     
